1. Field of the Invention
The present invention relates to a switch device, and, more specifically, to a switch device suitable to be used for driving an on-vehicle power window apparatus.
2. Description of the Related Art
A switch device in the related art will be described referring to attached drawings. FIG. 18 is an exploded perspective view showing the switch device in the related art, and FIG.19 is a cross sectional view showing the switch device in the related art.
The switch device in the related art is a so-called bipolar/double-throw switch device having two switch element sets.
An enclosure 81 includes a substantially box-shaped case 82 and a plurality of fixed contact members 83 formed in the case 82 of metallic material by insert molding so as to extend partly outward from the case 82.
The case 82 includes a bottom wall 82a, sidewalls 82b surrounding four sides, a partitioning wall 82c disposed in parallel with one of opposing sidewalls 82b, and two openings 82d formed on top of the sidewalls 82b and the partitioning wall 82c. 
The fixed contact member 83 includes a first, a second and a third fixed contact points (not shown). A first, a second and a third terminals 83a, 83b and 83c extend outward from the first, the second and the third fixed contact points (not shown) respectively.
The fixed contact member 83 is formed by insert molding on the bottom wall 82a of the case 82, so that the first, the second and the third fixed contact points (not shown) are partly exposed from the surface of the bottom wall 82a, and the first, the second and the third terminals 83a, 83b and 83c extend outward from one of the sidewalls 82b. 
Two (two pairs of) fixed contact members 83 are disposed symmetrically with respect to the case 82.
A movable contact member 84 is formed symmetrically in a substantially M-shape, and includes a first movable contact point 84a located at the center of the movable contact member 84. A second and a third movable contact points 84b and 84c are provided at both free ends so as to interpose the first movable contact point 84a therebetween.
The movable contact member 84 is disposed such that the first movable contact point 84a is in contact with the upper surface of the first fixed contact point (not shown), the second movable contact point 84b is opposed to the second fixed contact point (not shown), and the third movable contact point 84c is opposed to the third fixed contact point (not shown).
In other words, the movable contact member 84 is stored in the case 82.
Two pieces of the movable contact members 84 are respectively disposed on the fixed contact members 83 as described above.
The movable contact member 84 is further disposed so as to be capable of a seesaw movement about the first movable contact point 84a. 
A driving member 85 includes a substantially box-shaped base portion 85a and a pair of semi-cylindrical (semi-circular) driving portions 85b disposed at the lower end of the base portion 85a. 
The driving member 85 is disposed in such a manner that the distal ends of the driving portions 85b are in contact with the first movable contact points 84a at the center of the M-shaped movable contact members 84 respectively.
A lid member 86 includes a rectangular upper wall 86a, sidewalls 86b surrounding four sides of the upper wall 86a, mounting portions 86c extending upward from the center between the opposing sidewalls 86b, through holes 86d formed coaxially on the pair of mounting portions 86c in the vicinity of the upper ends thereof, and a rectangular opening 86e formed between the pair of mounting portions 86c. 
The lid member 86 engages the upper portion of the case 82 with suitable means such as snap engagement and the like so that the upper wall 86a thereof covers the two openings 82d of the case 82. In this case, the base portion 85a of the driving member 85 is disposed in the opening 86e of the lid member 86.
The spring member 87 is constructed of a coil spring, and the spring member 87 is disposed by suitable means in the base portion 85a of the driving member 85.
An operating tab member 88 includes a rectangular tab portion 88a, a rectangular storage section 88b extending downward from the center of the tab portion 88a and being surrounded along four sides, and a pair of cylindrical projections 88c projecting outward from one of the opposing outer surfaces of the storage section 88b. 
An operating tab member 88 is disposed in such a manner that the storage section 88b is inserted into the opening 86e of the lid member 86, and the driving member 85 provided with a spring member 87 is disposed in the storage section 88b. 
The pair of projections 88c of the operating tab member 88 are inserted into and attached to the respective through holes 86d. 
In this state, the driving portion 85b of the driving member 85 drives the first movable contact point 84a of the movable contact member 84 toward the first fixed contact point (not shown) of the fixed contact member 83 by a resilient force of the spring member 87.
The operating tab member 88 is adapted to be capable of a swinging motion (clockwise or counterclockwise) about the pair of projections 88c. This swinging motion of the operating tab member 88 allows the driving member 85 to swing.
By such swinging motion of the driving member 85, the pair of driving portions 85b of the driving member 85 brings the movable contact member 84 formed into an M-shape into a seesaw motion. Such seesaw motion of the movable contact member 84 brings the second or the third movable contact point 84b or 84c of the movable contact member 84 into and out of contact with the second or the third fixed contact point (not shown) of the fixed contact member 83.
However, in the switch device in the related art, a relatively large lid member is disposed on the case, and the operating tab member is attached on the lid member for a swinging motion. Therefore, it has a disadvantage in that the entire construction of the switch device is upsized.
In addition, the switch device in the related art is not cost-effective owing to its higher manufacturing cost due to its relatively large number of components and the greater number of steps required in assembly.
Further more, since the spring member has to be built in the operating tab member in advance, it is not easy to assemble.